A push-piece of this type is described in Swiss Pat. No. 423 638. The locking means are constituted by an outer collar mounted on the head of the push-piece by means of a screw-thread, the head comprising internal splines co-operating with splines on the tube, which enable the head to slide on the tube but prevent the latter from rotating. When the collar is screwed, the latter comes to bear against the watch case, thus immolizing the push-piece in the inoperative position.
In this previous construction, when diving, in the locked position, water is able to penetrate through the splines, without it being possible to stop the latter by means of a gasket. On the other hand, when in the locked position, the collar, bearing against the watch case, exerts traction on the tube. This makes it necessary to use a screwed tube, since there is a risk that a tube which is driven-in would be torn out.